Embodiments of the present invention generally relate to the field of integrated circuit fabrication, and more particularly to methods and apparatus for improving chemical vapor deposition, atomic layer deposition and other chemical reaction techniques.
An important consideration of formation of films on substrate surfaces containing dense metal oxides by chemical reaction techniques such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) is preparation of the metal oxide surface and the initiation process. As discussed herein, these considerations also apply to dense metal oxides such as porous metal oxides (including low-k films), which still need surface treatment techniques without significant penetration of aqueous solution. Surface preparation requires the substrate surface to be chemically activated to promote growth of the initial and subsequent layers on the substrate. The substrate surface can be prepared to provide a dense reactive species, for example, by hydroxylation.
SiO2 (silica) surfaces are not very reactive toward many precursors used in chemical reaction techniques to form layer because these surfaces have no reactive site or “chemical handle”. Typically, to make a surface more reactive it must be treated ex situ, that is, outside the process chamber environment, with harsh aqueous solutions such as SC-1 or chemox. These treatments generate surface hydroxyls which provide very good chemical handles for many subsequent precursors. One problem with this surface activation strategy is that it requires an air break from the process chamber(s) that are used to deposit subsequent layers, and this air break inherently leads to carbon contamination and poor device performance. Other problems may include relatively higher etching rate impacting SiO2 film thickness, and penetration of SC-1 aqueous solution to local device structure with porous film requirement. Other methods to activate silica surfaces include plasma treatments which can produce very reactive dangling bonds. Although plasma treatments, can be performed in situ (within the process chamber environment), these plasma treatments are difficult to control and lead to non-uniform surfaces. There is a need to provide methods to provide techniques that can be used in situ in the process chamber environment to provide reactive surfaces on dense thermal oxide surfaces.